1. Field of the Invention
The invention relates generally to code readers and particularly to readers which sense optically discernible symbol combinations or codes, such as bar codes.
2. Discussion of the Prior Art
1. Hand-held optical character reading equipment that has been available in the past has not performed well. The reader must be positioned accurately during the entire movement across the label for a valid read to occur. Operators usually xe2x80x9cscrubxe2x80x9d the label with the reader rather than carefully aligning the reader on the label, and often give up and manually key the information into the terminal.
The primary reason that accurate alignment is required is that the reader uses either a linear matrix of sensing elements, say sixty-four, or a rectangular matrix of sensing elements, say fourteen by forty. The recognition algorithms typically used in these systems assume that the sensor is oriented accurately over or across the character to be read with a misalignment of less than seven degrees typically specified. The operator""s guides for the present products instruct the operator to hold the reader exactly perpendicular, centered on the edge of the line to be read, not tilted, skewed, angled or rocked, and to hold this alignment during the sweep across the label. It is unsurprising that few operators use the readers in this way, and that poor read rates and dissatisfaction with the criticality of the reader alignment during scanning, have been serious problems.
2. To date, there doesn""t appear to be an optical character reader (OCR) product available that realistically has the capability to be operated portably. Power consumption and circuit complexity seem to be the factors that have discouraged development in this area.
3. While there was significant competition between the use of bar code and OCR systems through the late 1970""s, bar coding seems to have emerged as the preferred technology. It is quite likely that the reason for this xe2x80x9cwinxe2x80x9d is the poor performance of the available OCR equipment. If a very good, cost effective portable hand-held OCR reader were available, OCR might again become a contender for a significant share of this large market. The biggest factors in favor of an OCR system are that the label is directly human readable and the information density is high so that minimum label space is required for the information to be presented.
A basic concept of the invention is to provide a hand-held scanner which illuminates the entire width and height of a line or lines of code elements or characters on a label with a highly intense, short duration light pulse, then focusing the reflected area image through an optical lens system onto an imaging device, converting the sensed area signal to a digital signal which may then be stored, manipulated and processed by logic circuits as a complete area image to identify the information content.
In a preferred implementation of the hand-held area image scanner, the light source might be one or more xenon flash tubes arranged in a circumferential configuration to provide uniform illumination of the label surface. A lens system focuses an image of the entire label on the optical surface of the imaging device, preferably a solid state sensor of the charge coupled device type. With the proliferation of small, inexpensive consumer video cameras, very good, cost effective imaging devices of this type have become readily available. The output of the imaging device is converted to a digital signal which is interfaced to a digital processor for storage of the image pattern in memory. Once the information is contained in memory, processing and recognition algorithms may be performed xe2x80x9coff-linexe2x80x9d by the digital processor to rotate, normalize and enhance the image, remove xe2x80x9cnoisexe2x80x9d, and identify the coded information. A novel feature of this hand-held scanner is its ability to identify a broad set of optical information symbols including bar codes. Thus a hand-held reader may be configured that has the ability to read virtually any optically coded information while overcoming the long standing problems with prior hand-held OCR systems.
According to a teaching of the present invention, a hand-held optical reader has an area array of photosensor elements of size and resolution so as to register an entire line or multiple lines of characters at one time. Preferably, the entire field of symbols or characters or both, disposed on a label or the like is illuminated simultaneously by a brief flash of a highly intense light source. In a preferred implementation, a xenon flash tube of ring configuration surrounds the optical axis in the vicinity of a lens means which serves to focus the entire line or lines of code symbols or characters onto a complete image sensor array.
According to another aspect of the invention, alignment of the code configuration of symbols, characters or the like with the xe2x80x9cfield of viewxe2x80x9d of the reader may be achieved by orienting or pointing to position optical marker indicia. The marker indicia bracket or frame a sensing area delineated by the field of view of the reader, and impinge on a support surface peripherally about the region within which the code configuration is contained. The marker indicia are visually discernible impinging projections of marker beams which originate from marker type light sources of the reader.
According to a more specific aspect of the invention, the marker beams may be shaped by optical means to project linearly shaped marker spots as visually discernible indicia against an impinging surface, the linearly shaped indicia bounding the area within the field of view which will be focused on a photosensor array within the reader.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, and from the individual features of the appended claims.